1. Field of the Invention
The present invention relates to a write power determining method and write power control method for an optical disk drive, which sets write power for writing.
2. Description of the Related Art
Writable optical disk drives including a CD-R/RW drive, and a DVD-R/RW drive ensure the writing quality by the following control: OPC (Optimum Power control) which performs test writing of test data into a PCA area of an optical disk by use of various kinds of laser power, and then calculates laser power at which the reading quality such as a β value becomes a target value; and ROPC (Running Optimum Power Control) which feedback controls laser power so that a B value indicating the quantity of return light after a write pit is formed is kept constant independent of the irregularity of coating on a recording film in an optical disk surface and also independent of the inclination of the optical disk.
Because the ROPC performs the correction in a state in which various factors of the optical disk are mixed, it does not always achieve the optimization of the writing quality, and accordingly improvements are being tried in various ways.
For example, the following technologies are known: the laser power control that keeps the ratio of fluctuations in quantity of return light to fluctuations in laser power (ΔB/ΔP) in the ROPC constant so as to keep a β value constant irrespective of the inclination of the optical disk (for example, refer to patent document 1); the laser power control that keeps Bm/Pn constant (however, m<n) (for example, refer to patent document 2); and the like.
In addition, the following example of the running OPC (for example, refer to patent document 3) is known. To be more specific, if a phase change recording optical disk such as a CD-RW is used, when overwrite is performed onto a written area, it is influenced by a state of prior writing, which makes it difficult to ensure the writing quality in the ROPC. Therefore, the influence of the overwrite is eliminated by the following steps: dividing a laser light beam into a main beam (zero-order diffracted light) and two subbeams (+1 order diffracted light and −1 order diffracted light); while irradiating a groove track with the main beam to perform writing, irradiating each land track adjacent to both sides of the groove track with the two subbeams; and performing power control of the main beam by use of return light of the land track that is not influenced by the overwriting.
Moreover, in an optical disk drive, an optical pickup, which condenses a laser light beam and irradiates a track of an optical disk with a light spot to write information into the optical disk, is usually provided with divided light receiving elements which are disposed both in a track crossing direction of the light spot and in a direction orthogonal to the track crossing direction so that focus information and tracking information can be obtained from a detection signal coming from the divided light receiving elements.
After that, a push-pull signal (PP signal) is obtained by the subtraction of a detection signal coming from the divided light receiving element in the track crossing direction of the light spot, which is one of the divided light receiving elements. In addition to it, a differential phase detection signal (DPD signal) is obtained by the phase comparison of the detection signals coming from the divided light receiving elements. The slope angle of the optical disk is then detected by both of the signals (for example, refer to patent document 4). This is the known technology.
Patent document 1: Japanese Patent Laid-open No. 2003-16645 (claim 1, 0023)
Patent document 2: Japanese Patent Laid-open No. 2003-248929 (claim 1, claim 3, 0024, 0026)
Patent document 3: Japanese Patent Laid-open No. 2003-173533 (Abstract, claim 1, Disclosure of the invention, patent document 4)
Patent document 4: Japanese Patent Laid-open No. 2001-307359 (claim 1, claim 2, 0023 through 0028, and the like)